The Chehalis Gap is a gap in the Coast Range of Washington state between the southernmost foothills of the Olympic Mountains called the Satsop Hills, and the Willapa Hills. The gap is a major geographic feature of the northwestern United States. Other geographic features in the gap include Chehalis River, Grays Harbor, and Grays Harbor National Wildlife Refuge in its estuary. U.S. Route 12 runs through the gap from Elma near Capitol State Forest to Aberdeen on Grays Harbor near the coast, paralleled by the former U.S. Route 410 and Puget Sound and Pacific Railroad.